Process for producing highly crimped fibers



United States Patent ()fifice 3,419,652 PROCESS FOR PRODUCING HIGHLYCRIMPED FIBERS Masaichi Kubota, Atsushi Kawai, and Seiichi Omoto,Ohtake-shi, Japan, assignors to Mitsubishi Rayon Co., Ltd., Tokyo, JapanNo Drawing. Filed Sept. 1, 1964, Ser. No. 393,784 Claims priority,application Japan, Sept. 10, 1963, 38/ 47,835 16 Claims. (Cl. 264--168)ABSTRACT OF THE DISCLOSURE A process for producing highly crimpedviscose fibers which includes extruding a viscose containing at least 4%cellulose, and having a viscosity of from 100 to 1000 poises and a saltpoint of at least 16, into a coagulating bath containing zinc sulfate,formaldehyde and a small amount of sulfuric acid, stretching the thusformed fibers in an aqueous bath at a temperature of from 66 to 88 C.under substantially tensionless conditions, and relaxing the stretchedfibers in an aqueous bath at a temperature of from 30 to 70 C.

This invention relates to highly crimped viscose fibers having gooddimensional stability and nonuniform crosssectional structure and to aprocess for producing the fibers.

Conventional crimped viscose fibers have had a serious defect in thatthey have not been dimensionally stable. Moreover their crimpcharacteristics have not been satisfactory. Many attempts have beenproposed to overcome these defects, but none of them have heretoforebeen successful, especially with regard to dimensional stability.

Recently there have been developed high-wet-modulus fibers (polynosicfibers) which have improved dimensional stability. These fibers areproduced generally by extruding a viscose of high viscosity and of highgamma value into a coagulating bath of low acid and low salt content.Since coagulation of viscose is slow under these conditions, the crosssection of the fibers is circular and the cross-sectional structure isuniform. As in the case of conventional crimped viscose fibers, it ispossible to give polynosic fibers some extent of crimp by stretching thefibers as they emerge from a coagulating bath, cutting to staple lengthand then relaxing the fibers in an aqueous bath. However on account ofuniform cross-sectional structure, the percentage crimp thus obtained isgenerally less than 5 percent and it is difficult to make it more than 6percent. Moreover the crimp of these fibers is lost by applying only asmall load and the crimp cannot be re covered by removing the load.Accordingly it is essentially impossible for polynosic fibers to be usedas crimped fibers.

There is also another known process in which a viscose containingcellulose of a high degree of polymerization is extruded into acoagulating bath of low acid and low salt content, the extruded fibersare stretched progressively by passing several godet rolls and thestretched fibers are subjected to relaxation to develop crimp. Since thefibers obtained by this process have a uniform cross-sectionalstructure, they cannot develop satisfactory crimps. Moreover, thesefibers have a low knot strength. On account of these drawbacks, theyhave never been commercialized.

3,419,652 Patented Dec. 31, 1968 An object of the present invention is,accordingly, to provide a process for producing highly crimped viscosefibers having good dimensional stability and non-uniform cross-sectionalstructure. Another object of the present invention is to provide aprocess for producing viscose fibers of superior crimp, i.e., high crimpnumber, high percentage crimp and high crimp elasticity. A furtherobject of the present invention is to provide a process for producingviscose fibers having superior fiber properties.

These and other objects are attained in accordance with the presentinvention wherein a viscose which contains 4 weight percent ofcellulose, and has a viscosity of from 100 to 1000 poises and a saltindex (salt point) of more than 16, is extruded into a coagulating bathcontaining from 0.05 to 0.5 g./l. of zinc sulfate, from 10 to 250 g./l.of sodium sulfate and from 6 to 20 g./l. of formaldehyde and sulfuricacid having such a concentration as defined in the following formulas,the fibers thus formed are Withdrawn from said bath and stretched in abath of water or diluted aqueous acid solution at a temperature from 60C. to 88 C., under substantially tensionless conditions and to a percentstretch as defined in the following formulas and then, before or aftercutting into staple length, subjected to relaxation in a bath of wateror diluted aqueous acid solution at a temperature of from 30 C. to C. todevelop crimps.

Minimum concentration of sulfuric bath (g./l.)=2A+4 Maximumconcentration of sulfuric bath (g./1.)=7A+8 Minimum stretchpercent=2T+3.3F96

Maximum stretch percent=4T+6.6F144 acid in coagulating acid incoagulating wherein (percent) by weight in The fibers produced by thepresent invention have remarkably superior crimp characteristics. Forexample, they can have more than 12 crimps per inch, more than 9 percentcrimp and more than percent of crimp elasticity. Crimp stability isbetter than that of conventional crimped viscose staple fibers. Crimprecovery in Water is also superior. These superior properties are due tothe nonuniform structure of fiber cross section. It is surprising thatfibers produced at the extremely slow coagulating conditions of viscoseas in the present invention show the same nonuniform cross-sectionalstructure as those produced by the so called conjugate spinning process.As hereinafter described, such advantages can only be gained by aspecified combination of various conditions of the viscose, coagulatingbath, stretching bath and crimping bath, all of which are significantpoints of the present invention.

Fibers produced according to the present invention not only havesuperior crimp characteristics but also have exceedingly superiormechanical properties. This is, tenacity, elongation and wet modulus ofthe fibers are about the same as those of the latest known polynosicfibers. Dry

tenacity is about 4 g./d., wet tenacity is about 3 g./d., their dryelongation is about from to percent and their wet modulus is 1 g./d. ormore. Accordingly, the fibers produced by the present invention havegood dimensional stablity and can stand repeated washing. Knot strengthand abrasion resistance are also excellent. Water retention is about 70percent. This value is about the same or slightly higher than that oflatest polynosic fibers and it is a sufiicient value for waterresistance and dimensional stability. The fact is that the fibers of thepresent invention are not low in water retention dyeing properties. Itis a feature of the fibers of the present invention that the skin layeris biassed, the core is exposed to the outside and the fiber crosssectional structure is as nonuniform as that of the so-called conjugatespinning fibers. On account of their superior crimp characteristics andexcellent mechanical properties, the present fibers have goodspinability to yarn and can be used in a wide variety of fabrics with orwithout synthetic or cotton fibers. Fabrics converted from the presentfibers have comfortable hand, high slip-resistance, high dimensionalstability and superior mechanical properties.

A process having similarity to the present invention is I disclosed inJapanese Patent No. 452,141. This process relates to producing fibershaving dry tenacity of more than 5 g./d., wet tenacity of more than 4g./d., water retention of less than 55 percent and circularcross-sectional structure by extruding a viscose containing cellulose ofa high degree of polymerization, having high viscosity and high gammavalue into a coagulating bath of relatively low acid concentrationcontaining formaldehyde and subsequently subjecting the extruded fibersto a high extent of stretch in a hot aqueous bath. However, since thecrosssectional structure of the fibers produced by the abovementionedmethod is uniform, it is impossible to produce highly crimped fibers.Furthermore, fibers having a strength of more than 5 g./d., and waterretention of less than 55 percent cannot be obtained when the fibersextruded by the above-mentioned method are stretched under substantiallytensionless conditions. On the other hand, the present invention relatesto a process for producing highly crimped fibers having nonuniformcrosssectional structure using a specified viscose, coagulating bath andstretching conditions. It is impossible to produce the highly crimpedfibers of the present invention by use of the method of the Japanesepatent.

In the practice of the present invention, it is necessary that thecellulose concentration in the viscose is more than 4 percent by weight.When it is lower than 4 percent, development of crimps is notsatisfactory. Preferable cellulose concentration is from 6 to 10 percentby weight. The alkali concentration in the viscose is preferably from 2to 8 percent by weight and more preferably from 3 to 6 percent byWeight. The ratio of alkali to cellulose is particularly preferable whenit is in the range of from 0.521 to 0.7: 1. The viscosity of the viscosemust be in the range of from 100 to 1000 poises. Beyond this range,development of crimps is not satisfactory. Most preferably, theviscosity is from 200 to 700 poises. In the present invention it ispossible to produce highly crimped viscose fibers having superiormechanical properties without employing cellulose of an especially highdegree of polymerization. The salt index of the viscose to be used inspinning must be higher than 16. With a value less than 16, satisfactorycrimp development cannot be obtained. Most preferably, the salt index isfrom to 23.

The coagulating bath must contain sulfuric acid, sodium sulfate, Zincsulfate and formaldehyde.

The concentration of sulfuric acid is calculated in accordance with theconcentration of alkali in the viscose. When the alkali concentration inthe viscose is A (percent), the sulfuric acid concentration must be inthe following range:

Minimum sulfuric acid concentration g./l. =2A +4 Maximum sulfuric acidconcentration (g./l.) =7A+ 8 For fibers having deniers of 2 or less than2, it is preferable to use the following range of sulfuric acidconcentration:

Minimum sulfuric acid concentration (g./l.) =2A+4 Maximum sulfuric acidconcentration (g./l.) =3A+8 and for fibers having deniers more than 2,it is preferable to use the following range of sulfuric acidconcentration:

Minimum sulfuric acid concentration (g. /l.) =4A+4 Maximum sulfuric acidconcentration (g./l.) =7A+8 At a concentration lower than theabove-defined range, development of crimps is not satisfactory andspinning operations are difiicult. At a concentration higher than thatrange, deveolpment of crimps become impossible.

The concentration of sodium sulfate must be from 10 to 250 g./l.,preferably from 50 to g./l. for fibers having deniers of 2 or less than2 and preferably from to g./l. for fibers having deniers of more than 2.The concentration of zinc sulfate must be from 0.05 to 0.5 g./l. Whenthe coagulating bath contains less than 0.0 5 g./l. of zinc sulfate orit does not contain zinc sulfate at all, the development of crimpsbecomes insufficient and When the bath contains higher than 0.5 g./l. ofZinc sulfate extruded fibers stick together and thus, crimps can not bedeveloped. Most preferably, the concentration of zinc sulfate is from0.1 to 0.3 g./l. It is possible to replace Zinc sulfate with cadmium,sulfate or nickel sulfate but ammonium sulfate or magnesium sulfate isnot effective.

The formaldehyde concentration must be from 6 to 20 g./l. Atconcentrations lower than 6 g./ 1., develop- Inent of crimps is notsufficient and at concentrations higher than 20 g./l., crimp developmentbecomes insufficient. Most preferably, the concentration of formaldehydeis from8 to 15 g./l.

The temperature of coagulating bath is preferably from 15 C. to 25 C.The length of immersion in the coagulating bath is suitably in the rangeof from 20 cm. to 60 cm. Fibers emerging from the coagulating bath cannot develop sufficient crimps unless they are stretched under conditionsof high gamma value. When the gamma value of the viscose to be spun is78, the gamma value of fibers emerging from the coagulating bath is from60 to 75 to be most suitable. The preferred gamma value of fibersemerging from the coagulating bath for the development of crimps is inthe range of 60 to 80.

Fibers emerging from the coagulating bath are subjected to stretching inan aqueous stretching bath. The temperature of the stretching bath must'be from 60 C. to 88 C. If it is outside this range, suflicient crimpscannot be developed. A particularly preferred temperature of thestretching bath is from 70 C. to 83 C. A water bath may be used but anaqueous bath containing a low concentration of sulfuric acid ispreferably used as the stretching bath. An aqueous bath containingsulfuric acid salts may also be used. A stretching bath having asulfuric acid content of about 10 g./l. is most preferable. The percentstretch in the stretching bath is dependent upon the temperature of thestretching bath and the formaldehyde concentration in the coagulatingbath.

The upper and lower limits of the percent stretch are decided accordingto the following formulas, in which T C.) is the temperature of thestretching bath, and F (g./-l.) is the concentration of formaldehyde inthe coagulating bath.

Minimum stretch (percent)=2T-]-3.3F-96 Maximum stretch (percent)=4T+6.6F 144 Maximum stretch (percent) is preferably 3T+6.6F-128 forfibers having deniers of 2 or less than 2.

The above two formulas have been empirically derived from manyexperimental results. When the percent stretch deviates from the upperand low limits defined in the above formulas, development of crimpsbecomes difficult. The tension applied to the fibers in the stretchingbath is not more than 0.2 g./d. and preferably, it is from 0.05 to 0.02g./d. This is a significant point of the present invention. When thestretching tension exceeds 0.2 g./d. it is impossible to produce fibershaving non-uniform cross-sectional structure and accordingly it isimpossible to develop crimps.

The fibers stretched as described above are subjected to relaxation inan aqueous bath to develop crimps. The temperature of the relaxationbath must be in the range of from 30 C. to 70 C. Outside this range,development of crimps becomes insufiicient and properties of resultingfibers are poor. Preferably, the temperature of the relaxation bath isfrom 40 C. to 60 C. The relaxation bath can be water for a dilutedacidic aqueous bath. The fibers may be treated with a diluted acidicsolution at a temperature higher than 70 C. to complete regenerationafter development of crimps. The fibers may be cut to staple lengthafter development of crimps but are preferably out before development ofcrimps.

If the crimped fibers obtained by the present invention are treated withfrom 2 to 4 percent by weight of a dilute aqueous sodium hydroxidesolution at room temperature after completing regeneration, the crimpcharacteristics may be improved.

The invention is illustrated by the following examples.

EXAMPLE 1 Wood pulp sheets were steeped in 17.5 weight percent aqueouscaustic soda solution at a temperature of 20 C. for 1 hour and squeezedout to a weight 2.8 times the original weight of pulp. Then the squeezedout pulp sheets were shredded at a temperature of 20 C. for 1 hour toobtain crumbs of alkali cellulose. After ageing, the alkali cellulosewas added to 55 percent, based upon the weight of cellulose, of carbondisulfide. After xanthation at a temperature of 26 C. for 2 hours, thexanthated alkali cellulose was dissolved in aqueous caustic sodasolution and water, whereby viscose containing 8 percent by weight ofcellulose and 4 percent by weight of alkali was produced. The degree ofpolymerization of cellulose in the viscose was 360. a

After being filtered, this viscose was cooled, deaerated, ripened, andextruded through spinnerets at a viscosity of 250 poises, a salt indexof 20 and a gamma value of 80 into a coagulating bath containing 14-g./l. of sulfuric acid, 75 g./l. of sodium sulfate, 0.2 g./l. of zincsulfate and 14 g./l. of formaldehyde at a temperature of 20 C. Thelength of bath immersion was 33 cm. and the gamma value of fibersemerging from the coagulating bath was 64. The fibers were stretched to150 percent of their original length, namely to a stretch ratio of2.50:1, in a second bath containing 10 g./l. of sulfuric acid at atemperature of 80 C., cut to staple and subjected to relaxation in acrimping bath containing 10 g./l. of sulfuric acid at a temperature of50 C. to develop crimps. The crimped fibers were subjected to aconvention-a1 refining process. The properties and characteristics ofthe resulting fibers were as follows.

Denier d 1.9 Dry tenacity g./d 4.2 Wet tenacity g./d 3.2 Dry elongationpercent 12 Wet elongation do 16 Dry knot strength g./d 2.4 Water tensionpercent 73 Wet modulus g./d 1.8 Number of crimps per inch Percentagecrimp 9 Crimp elasticity percent 90 EXAMPLE 2 After aging, alkalicellulose produced by a conventional method was added to 55 percent,based upon the weight of cellulose, of carbon disulfide and afterxanthation at a temperature of 26 C. for 2 hours, the resulting xanthatewas dissolved in aqueous caustic soda solution and water whereby viscosecontaining 8 percent of cellulose and 4 percent of alkali was obtained.

The resulting viscose was filtered, cooled, deaerated, ripened andextruded at a viscosity of 500 poises and a salt index of 20, into acoagulating bath containing 16 g./l. of sulfuric acid, 75 g./l. ofsodium sulfate, 0.2 g./l. of zinc sulfate and 8 g./l. of formaldehyde ata temperature of 25 C. The length of bath immersion was 30 cm. and thegamma value of fibers emerging from the coagulating bath was 66. Thefibers were cut to staple length and subjected to a stretching andrelaxation treatment under the same conditions as in Example 1 to obtaincrimped fibers. The properties and crimp characteristics of theresulting fibers were as follows.

Denier d 2 Dry tenacity g./d 4.3 Wet tenacity 'g./d 3.3 Dry elongationpercent 10 Wet elongation do 14 Dry knot strength g./d 21 Waterretention percent Number of crimps per inch 15 Percentage crimp 9 Crimpelasticity percent 83 EXAMPLE 3 Viscose produced by the method ofExample 1 was extruded into a coagulating bath containing 14 g./l. ofsulfuric acid, g./l. of sodium sulfate, 0.2 g./l. of zinc sulfate and 8g./l. of formaldehyde at a temperature of 25 C. Fibers emerging from thecoagulating bath were stretched percent in a second bath containing 10g./l. of sulfuric acid at a temperature of 70 C., cut to staple andsubjected to relaxation in a crimping :bath containing 10 g./l. ofsulfuric acid at a temperature of 50 C. to develop crimps, and to aconventional refining process. The properties and crimp characteristicsof resulting fibers were as follows.

Denier d 1.9 Dry tenacity g./d 3.5 Wet tenacity g./d 2.7 Dry elongationpercent 11 Wet elongation do 15 Dry knot strength g./d 1.6 Water tensionpercent 72 Wet modulus g./d 1.6 Number of crimps per inch 17 Percentagecrimp 15 Crimp elasticity percent 75 The fibers produced according tothe method of Example 3 were cut into sections and the sections wereskindyed. Some sections of the fibers were core-dyed.

Skin dyeing was conducted in an aqueous solution containing 1 percent byweight of J apanol Brilliant Blue 6 BKX (C.I. Direct Blue 1) and 10percent by weight of sodium chloride at a temperature of 100 C. for 30minutes, followed by decoloration of the core and dehydration.

Core dyeing was conducted in an aqueous solution containing 1 percent byweight of Solophenyl Fast Blue Green BL (C.I. Direct Green 27) and. 0.3percent by Weight of sodium sulfate at room temperature for 5 hours,followed by washing with water.

EXAMPLE 4 Alkali cellulose produced by a conventional method wassubjected to aging, added to 57 percent, based upon the weight ofcellulose, of carbon disulfide, xanthated at a temperature of 26 C. for2 hours and dissolved in an 1 aqueous caustic soda solution and water toobtain viscose containing 7 percent by weight of cellulose and 4 percentby weight of alkali.

EXAMPLE 5 Viscose produced by the same conditions as in Example 4 togive a salt index of 20, was extruded into a coagulating bath containing15 g./l. of sulfuric acid, 75 g./l. of sodium sulfate, 0.2 g./l. of zincsulfate and 10 g./l. of formaldehyde. Fibers emerging from thecoagulating bath were stretched 125 percent in a second bath containing10 g./l. of sulfuric acid at a temperature of 70 C., cut to staplelength and subjected to relaxation to develop crimps in a crimping bathcontaining 10 g./l. of sulfuric acid at a temperature of 50 C. and to aconventional refining process. As controls, spinning was performed atthe same conditions as in the present example except that coagulatingbath containing 0.5 g./1. of zinc sulfate or no zinc sulfate was used.The properties of the resulting fibers were as follows. When theconcentration of zinc sulfate became 1 g./l., fibers stuck together andno crimps were developed.

Concen- Dry Wet Dry tration of Denier tenacity tenacity elongation zincsul- ((1.) (g./d.) (EL/ti.) (percent) fate (g./l.)

Present invention 0.2 2 3.8 2. 9 11 C ontrol 2 3. 3 2. 5 D0 0. 5 2 3. 62. 4 10 Wet Dry knot Number Percentage Crimp elongation strength ofcrimps crimp elasticity (percent) (g./d.) per inch (percent) (percent)Present invention-.. 13 1. 8 12 79 Control 13 1. 4 7 5 83 12 1. 3 9 6 80EXAMPLE 6 This viscose was filtered, cooled, deaerated, ripened andextruded at a viscosity of 250 poises, salt index of and gamma value of87, into a coagulating bath containing 15 g./l. of sulfuric acid, 75g./l. of sodium sulfate, 0.2 g./l. of zinc sulfate and 10 g./l. offormaldehyde, at a temperature of 20 C. Fibers emerging from thecoagulating bath were stretched 125 percent in a second bath containing10 g./l. of sulfuric acid at a temperature of 70 C., out to staplelength and subjected to relaxation in a crimping bath containing 10g./l. of sulfuric acid at a temperature of 50 C. to develop crimps andto a conventional refining process. Crimp characteristics of theresulting fibers were as follows. As a control, fibers were produced bythe same conditions as in Example 4 except that viscose ripened at 14 C.and having a salt index of 15 was used. The properties of the resultingfibers were very much the same as in Example 4. Crimp characteristics inboth the cases were as follows.

Viscose produced according to the same method as in Example 4 wasextruded into a coagulating bath containing 18 g./l. of sulfuric acid,125 g./l. of sodium sulfate, 0.2 g./l. of zinc sulfate and 10 g./l. offormaldehyde at a temperature of 20 C. Fibers emerging from thecoagulating bath were stretched 175 percent in a second bath containing10 g./l. of sulfuric acid at a temperature of 85 C., cut to staplelength and subjected to relaxation in a crimping bath containing 10g./l. of sulfuric acid at a temperature of 50 C. to develop crimps andto a conventional refining process. The properties and crimpcharacteristics of the resulting fibers are shown in the followingtable. The properties and crimp characteristics of controls producedaccording to the same conditions except that the concentration of sodiumsulfate was 280 g./l. are also shown in the same table. When thecoagulating bath did not contain sodium sulfate, fibers stuck togetherand no crimps were developed.

Salt Number Percentage Crimp index of crimps crimp elasticity per inch(percent) (percent) Present invention- 20 15 11 79 Control 15 7 5 83Sections of fibers produced according to the present example were dyedas in Example 3.

EXAMPLE 7 The same viscose as in Example 4 was extruded into acoagulating bath containing 18 g./l. of sulfuric acid, 50

g./l. of sodium sulfate, 0.2 g./l. of zinc sulfate and 10 g./l. offormaldehyde at a temperature of 20 C. Fibers emerging from thecoagulating bath were stretched 150 percent in a second bath containing10 g./l. of sulfuric acid at a temperature of 80 C., out to staplelength and subjected to relaxation in a crimping bath containing 10g./l. of sulfuric acid at a temperature of 50 C. and to a conventionalrefining process. The properties and crimp characteristics of resultingfibers are shown in the following table. The properties and crimpcharacteristics of a control produced by the same method as in thepresent example except that the concentration of formaldehyde was 5g./l. are also shown in the same table.

1 0 EXAMPLE 9 The same viscose as in Example 4 was extruded into acoagulating bath containing 16 g./l. of sulfuric acid, 75 g./l. ofsodium sulfate, 0.2 g./l. of zinc sulfate and 8 g./l. of formaldehyde ata temperature of 20 C. Fibers emerging from the coagulating bath werestretched.150 percent in a second bath containing 10 g./l. of sulfuricacid at a temperature of 80 C., out to staple length and subjected torelaxation in a crimping bath at a temperature of 50 C. to developcrimps and to a conventional refining process. In this instance there isa certain relation between the stretching conditions and tension of thefibers in the second bath. Tension is also 0 when stretching is Formal-When the concentration of formaldehyde became higher than g./l., fibersstuck together.

110 percent, 0.02 g./d. when stretching is 150 percent.

and 0.4 g./d. when stretching is 300 percent. The properties and crimpcharacteristics of these fibers are as follows Stretch Tension DenierDry Wet Dry (percent) (g./tl.) (d.) tenacity tenacity elongation (g./d.)(g./d.) (percent) Present invention 110 0. 005 2 3. 5 2. 5 13 150 0.02 23. 9 3. 0 10 300 0. 6 2 5. 5 4. 6 8

Wet Dry knot Number Percentage Crimp elongation strength of crimps crimpelasticity (percent) (g./d.) per inch (percent) (percent) Presentinvention 15 1. 5 17 15 78 Do l3 1. 8 14 12 85 Control 9 2. 2 3 2 95EXAMPLE 8 EXAMPLE 10 The same viscose as in Example 4 was extruded intoa coagulating bath containing 18 g./l. of sulfuric acid, 75 g./l. ofsodium sulfate, 0.2 g./l. of zinc sulfate and 10 g./l. of formaldehydeat a temperature of 20 C. Fibers emerging from the coagulating bath:were stretched 150 percent in a second bath containing 10 g./l. ofsulfuric acid at a temperature of 80 C., cut to staple length andsubjected to relaxation in a crimping bath containing 10 g./l. ofsulfuric acid at a temperature of C. to develop crimps and to aconventional refining process. The properties and crimp characteristicsof the resulting fibers together with those of controls produced by thesame conditions as in the present example except that sulfuric acidconcentrations were 11 g./l. and 38 g./l. respectively, are shown in thefollowing table.

Viscose prepared under the same conditions as in Example 1 was extrudedinto a coagulating bath containing 16 g./l. of sulfuric acid, g./l. ofsodium sulfate, 0.2 g./l. of zinc sulfate and 10 g./l. of formaldehydeat a temperature of 20 C. Fibers emerging from the coagulating bath,were stretched percent in a second bath containing 10 g./1. of sulfuricacid at a temperature of 70 C., cut to staple length and subjected. torelaxation in a crimping bath containing 10 g./l. of sulfuric acid at atemperature of 50 C. to develop crimps and to a conventional refiningprocess. The properties and crimp characteristics of resulting fibersare shown in the following table. The properties and crimpcharacteristics of fibers crimped at a temperature higher or lower thanthose in the present example are added to the table. When thetemperatures of the crimping bath is higher than 70 C., fibers sticktogether.

temperature of 70 C., cut to staple length and subjected to relaxationin a crimping bath containing g./l. of sul- Temperature of Denier DryWet Dry Crimping (tl.) tenacity tenacity elongation bath (g./d.) (g./d.)(percent) Present invention 50 2 3.8 2. 9 10 20 2 2.6 1.9 9 70 2 2.4 1.611

Wet Dry knot Number Percentage Crimp elongation strength of crimps crimpelasticity (percent) (g./t1.) per inch (percent) (percent) Presentinvention 12 1. 7 14 12 85 11 1.5 12 11 87 12 1.3 14 15 83 EXAMPLE 11furic acid at a temperature of 50 C. to develop crimps Viscose preparedunder the same conditions as in Example 4 Was extruded into acoagulating bath containing 16 g./l. of sulfuric acid, 75 g./l. ofsodium sulfate, 0.2 g./l. of zinc sulfate and 10 g./l. of formaldehydeat a temperature of 23 C. Fibers emerging from the coagulating bath werestretched 150 percent in a second bath containing 10 g./l. of sulfuricacid at a temperature of 80 C. cut to staple length and subjected torelaxation in a crimping bath containing 10 g./l. of sulfuric acid at atemperature of 50 C. to develop crimps and to a conventional refiningprocess. Sections prepared from the resulting fibers were skindyed as inExample 3. As controls, nonstretched fibers and fibers stretched by 350percent were likewise skindyed.

EXAMPLE 12 Viscose produced by the same conditions as in Example 4 togive a slat index of 20, a gamma value of 87 and a viscosity 300 poiseswas extruded into a coagulating bath containing 27 g./l. of sulfuricacid, 150 g./l. of sodium sulfate, 0.2 g./l. of zinc sulfate and 14g./l. of formaldehyde at a temperature of C. The fibers emerging fromthe coagulating bath were stretched 150 percent in a second bathcontaining 10 g./l. of sulfuric acid at a temperature of 70 C., cut tostaple length and subjected to relaxation in a crimping bath containing10 g./l. of sulfuric acid at a temperature of 50 C. to develop crimpsand to a conventional refining process. The properties and crimpcharacteristics of resulting fibers and conventional crimped fibers areas follows:

and a conventional refining process. The properties and crimpcharacteristics of the resulting fibers are shown as follows.

Denier d 5.2 Dry tenacity g./d 3.4 Wet tenacity g./d 2.5 Dry elongationpercent 14 Wet elongation percent 15 Dry knot tenacity g./d 1.3 Numberof crimps per inch 10 Percentage crimp percent 19 Crimp elasticitypercent 84 As control, spinning was performed under the same conditionsas in this example except that a coagulating bath contaninig 0.5 -g./l.of zinc sulfate or no zinc sulfate was used. In these cases, developmentof crimps was insufficient. When the coagulating bath contained morethan 1 g./l. of zinc sulfate, resulting fibers stuck together and thusdevelopment of crimps was also insufficient.

EXAMPLE 14 Viscose produced by the same conditions as in Example 4 wasextruded into a coagulating bath containing 30 g./l. of sulfuric acid,150 g./l. of sodium sulfate, 0.2 g./l. of zinc sulfate and 10 g./l. offormaldehyde at a temperature of 20 C. The fibers emerged from thecoagulating bath were stretched 175 percent in a second bath containing10 g./l. of sulfuric acid at a temperature of 73 0, cut to staple andsubjected to relaxation in a Alkali cellulose produced by the samemethod as in Example 4 was aged, added to percent, based upon the Weightof cellulose, of carbon disulfide, xanthated for 2 hours at atemperature of 26 C. and dissolved in an aqueous caustic soda solutionand water to give a viscose containing 8 percent by weight of celluloseand 4 percent by weight of alkali. The viscose was filtered, cooled,deaerateld, ripened rand extruded through spinnerets at a viscosity of400 poises and a salt index of 20 g. into a coagulating bath containing30 g./l. of sulfuric acid, 150 g./l. of sodium sulfate, 0.2 g./l. ofzinc sulfate and 12 g./1. of formaldehyde at a temperature of 20 C.Fibers emerging from the coagulating bath were stretched 150 percent ina second bath containing 10 g./l. of sulfuric acid at a crimping bathcontaining 10 g./l. of sulfuric acid at a temperature of 50 C. andconventional refining process. The properties and crimp characteristicsof resulting fibers were as follows:

Denier d 5.0 Dry tenacity g./d- 3.8 Wet tenacity g./d 2.9 Dry elongation"percent" 11 Wet elongation percent 12 Dry knot tenacity g./d 1.5 Wetmodulus g./d 1.6 Number of crimps per inch 10 Percentage crimp percent15 Crimp elasticity "percent..- 89

As control, spinning was performed at the same conditions as in thisexample except that the coagulating bath containing 75 g./l. of sodiumsulfate was used. In this case, resulting fibers of deniers sticktogether and thus development of crimps was insutficient. When thecoagulating bath containing more than 250 g./l. of sodium sulfate,development of crimps was also insufficient.

We claim:

1. A process for producing highly crirnped viscose fibers whichcomprises extruding a viscose containing at least 4 percent cellulose,said viscose having a viscosity of from 100 to 1000 poises and a saltpoint of at least 16, into a coagulating bath containing from 0.05 to0.5 g./l. zinc sulfate, from to 250 g./l. sodium sulfate, from 6 tog./l. formaldehyde and a concentration of sulfuric acid of from 2A+4 to7A+8 wherein A is the alkali concentration in the viscose in percent byweight, withdrawing the fibers thus formed from the coagulating bath andstretching said fibers in an aqueous bath at a temperature of from 60 C.to 88 C. under substantially tensionless conditions to the extentdefined in the following formulas:

Minimum stretch percent=2T+3.3F96 Maximum stretch percent=4T+ 6.6F- 144wherein T is the temperature of the stretching bath C.), and

F is the concentration of formaldehyde (g./l.) in the cogulating bath,

and subsequently subjecting the stretched fibers to relaxation in anaqueous bath at a temeprature of from 30 C. to 70 C. to develop crimps.

2. The process according to claim 1 wherein the stretched filaments arecut to staple length before being subjected to relaxation.

3. The process according to claim 2 wherein the fibers are subjected tocomplete regeneration in an aqueous acidic solution at a temperature ofat least 70 C. and then to treatment in an aqueous alkaline solution.

4. The process according to claim 1 wherein the relaxed fibers aresubjected to complete regeneration in an aqueous acidic solution at atemperature of at least 70 C.

5. The process according to claim 1 wherein the cellulose concentrationin the viscose is from 6 to 10 percent, the alkali concentration in theviscose is from 3 to 5 percent, the viscosity of the viscose is from 200to 700 poises, the salt point of the viscose is from 20 to 23 and the degree of polymerization of the cellulose in the viscose is from 300 to600.

6. The process according to claim 1 wherein the coagulating bathcontains from 0.05 to 0.4 g./l. of zinc sulfate, from 10 to 100 g./l. ofsodium sulfate, from 6 to 15 g./l. of formaldehyde and a concentrationof sulfuric acid of from 2A+4 to 3A+8.

14 7. The process according to claim 6 wherein the percent stretch isdefined by the following formulas:

Minimum stretch percent=2T-|-3.3F96 Maximum stretch percent=3T+6.6F--l288. The process according to claim 1 wherein the coagulating bathcontains from 0.1 to 0.3 g./l. of zinc sulfate, from 50 to g./l. ofsodium sulfate, from 8 to 14 g./l. of formaldehyde and a concentrationof sulfuric acid of from 2A+4 to 3A+ 8.

9. The process according to claim 1 wherein the coagulating bathcontains from 0.05 to 0.5 g./l. of zinc sulfate, from to 250 g./l. ofsodium sulfate, from 6 to 20 g./l. of formaldehyde and a concentrationof sulfuric acid of from 4A+4 to 7A+8.

10. The process according to claim 9 wherein the percent stretch isdefined by the following formulas:

Minimum stretch ratio percent=2T+3.3F-96 Maximum stretch ratiopercent=4T+6.6F-144 11. The process according to claim 1 wherein thecoagulating bath contains from 0.1 to 0.3 g./l. of zinc sulfate, from tog./l. of sodium sulfate, from 10 to 16 g./-l. of formaldehyde and aconcentration of sulfuric acid of from 4A+4 to 7A+8.

12. The process according to claim 1 wherein the temperatuer of thecoagulating is from 15 C. to 25 C.

13. The process according to claim 1 wherein the tension applied to thefibers in the stretching bath does not exceed 0.2 g./d.

14. The process according to claim 1 wherein the tension applied to thefibers in the stretching bath does not exceed 0.1 g./d.

15. The process according to claim 1 wherein the tension applied to thefibers in the stretching bath is from 0.005 to 0.02 g./d.

16. The process according to claim 1 wherein the temperature ofstretching bath is from 70 C. to 83 C.

References Cited UNITED STATES PATENTS 3,046,083 7/1962 Bates et a1.264-168 3,107,970 10/1963 Kusunose et a1. 264197 3,108,849 10/1963 Owashet a1. 264-198 3,109,698 11/1963 Klein et al. 3,226,461 12/1965 Wise eta1. 264-- X DONALD J. ARNOLD, Primary Examiner. J. H. WOO, AssistantExaminer.

US. Cl. X.R.

